Use of renewable energies is increasing because of the limited supply of coal, petroleum products and other hydrocarbons. Renewable energy sources are green and environmentally friendly. Among the renewable energies, solar energy is freely and abundantly available.
Various commonly used devices are operable with solar energy. For example, solar calculators are very common. In addition to solar energy, these calculators work under any source of light energy. Similarly wrist watches are also available that work under light energy of any kind. Solar and other light energies are useful for several applications, from powering space stations to many household appliances.
Photovoltaic systems use solar radiation—both direct and scattered sunlight—to create electrical energy. The basic building blocks of a photovoltaic system are solar/photovoltaic cells. The cells typically consist of semiconductor materials that convert light into electricity. In order to increase power output, a plurality of cells can be interconnected to form panels or modules. The panels are typically flat. Several modules can be installed in a rack to form a photovoltaic array. Photovoltaic systems further include mounting racks and hardware for the panels, wiring for electrical connections, and power conditioning equipment, including inverters and optional batteries for electricity storage.
The energy conversion efficiency or ECE (η) of the cells is the percentage of the incident photon energy in the form of sunlight or any other source of light that is converted to electrical energy. When a photon penetrates a photovoltaic cell, it can produce an electron-hole pair. The pair generated may contribute to the current produced by the cell or may recombine with no net contribution to cell current.